我有一个scala程序,我已经实现了一个完美的二级排序。我编写该程序的方式是:
object rfmc {
// Custom Key and partitioner
case class RFMCKey(cId: String, R: Double, F: Double, M: Double, C: Double)
class RFMCPartitioner(partitions: Int) extends Partitioner {
require(partitions >= 0, "Number of partitions ($partitions) cannot be negative.")
override def numPartitions: Int = partitions
override def getPartition(key: Any): Int = {
val k = key.asInstanceOf[RFMCKey]
k.cId.hashCode() % numPartitions
}
}
object RFMCKey {
implicit def orderingBycId[A <: RFMCKey] : Ordering[A] = {
Ordering.by(k => (k.R, k.F * -1, k.M * -1, k.C * -1))
}
}
// The body of the code
//
//
val x = rdd.map(RFMCKey(cust,r,f,m,c), r+","+f+","+m+","+c)
val y = x.repartitionAndSortWithinPartitions(new RFMCPartitioner(1))
}
我想用clojure的DSL实现同样的东西,称为flambo。由于我无法使用clojure编写分区器,因此我重新使用上面的代码定义,编译它并将其用作我的Clojure代码中的依赖项。
现在我按照以下方式在clojure代码中导入分区器和键:
(ns xyz
(:import
[package RFMCPartitioner]
[package RFMCKey]
)
)
但是当我尝试通过RFMCKey
创建(RFMCKey. cust_id r f m c)
时,会抛出以下错误:
java.lang.ClassCastException: org.formcept.wisdom.RFMCKey cannot be cast to java.lang.Comparable
at org.spark-project.guava.collect.NaturalOrdering.compare(NaturalOrdering.java:28)
at scala.math.LowPriorityOrderingImplicits$$anon$7.compare(Ordering.scala:153)
at org.apache.spark.util.collection.ExternalSorter$$anon$8.compare(ExternalSorter.scala:170)
at org.apache.spark.util.collection.ExternalSorter$$anon$8.compare(ExternalSorter.scala:164)
at org.apache.spark.util.collection.TimSort.countRunAndMakeAscending(TimSort.java:252)
at org.apache.spark.util.collection.TimSort.sort(TimSort.java:110)
at org.apache.spark.util.collection.Sorter.sort(Sorter.scala:37)
at org.apache.spark.util.collection.SizeTrackingPairBuffer.destructiveSortedIterator(SizeTrackingPairBuffer.scala:83)
at org.apache.spark.util.collection.ExternalSorter.partitionedIterator(ExternalSorter.scala:687)
at org.apache.spark.util.collection.ExternalSorter.iterator(ExternalSorter.scala:705)
at org.apache.spark.shuffle.hash.HashShuffleReader.read(HashShuffleReader.scala:64)
at org.apache.spark.rdd.ShuffledRDD.compute(ShuffledRDD.scala:92)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:277)
at org.apache.spark.CacheManager.getOrCompute(CacheManager.scala:70)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:242)
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:35)
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:277)
at org.apache.spark.rdd.RDD.iterator(RDD.scala:244)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:61)
at org.apache.spark.scheduler.Task.run(Task.scala:64)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:203)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
我的猜测是它无法找到我在分区后定义的顺序。但如果它在Scala中有效,为什么它在Clojure中不起作用?
答案 0 :(得分:0)
所以我终于把它弄清楚了。我必须基本上将自定义排序函数编写为单独的scala项目,然后在clojure中调用它。
我以这种方式编写了我的scala文件:
import org.apache.spark.Partitioner
import org.apache.spark.rdd.RDD
case class RFMCKey(cId: String, R: Double, F: Long, M: Double, C: Double)
class RFMCPartitioner(partitions: Int) extends Partitioner {
require(partitions >= 0, "Number of partitions ($partitions) cannot be negative.")
override def numPartitions: Int = partitions
override def getPartition(key: Any): Int = {
val k = key.asInstanceOf[RFMCKey]
k.cId.hashCode() % numPartitions
}
}
object RFMCKey {
implicit def orderingBycId[A <: RFMCKey] : Ordering[A] = {
Ordering.by(k => (k.R, k.F * -1, k.M * -1, k.C * -1))
}
}
class rfmcSort {
def sortWithRFMC(a: RDD[(String, (((Double, Long), Double), Double))], parts: Int): RDD[(RFMCKey, String)] = {
val x = a.map(v => v match {
case (custId, (((rVal, fVal), mVal),cVal)) => (RFMCKey(custId, rVal, fVal, mVal, cVal), rVal+","+fVal+","+mVal+","+cVal)
}).repartitionAndSortWithinPartitions(new RFMCPartitioner(parts))
x
}
}
我将它编译为ascala项目并以这种方式在我的clojure代码中使用它:
(:import [org.formcept.wisdom rfmcSort]
[org.apache.spark.rdd.RDD])
sorted-rfmc-records (.toJavaRDD (.sortWithRFMC (rfmcSort.) (.rdd rfmc-records) num_partitions))
请注意我从我创建的sortWithRFMC
对象调用rfmcSort
函数的方式。此处需要注意的一件非常重要的事情是,当您将JavaPairRDD
传递给scala函数时,必须首先通过调用spark RDD
方法将其转换为普通.rdd
。然后你必须将spark RDD
转换回JavaPairRDD
以便在clojure中使用它。